Improving hash join performance through prefetching. Our simulations indicate that an approach combining. In addition, parallel io enhances prefetching efficiency. When prefetching works, when it doesnt, and why jaekyu lee, hyesoon kim, and richard vuduc, georgia institute of technology in emerging and future highend processor systems, tolerating increasing cache miss latency and properly managing memory bandwidth will be critical to achieving high performance. A survey of data prefetching techniques semantic scholar.
For the sake of brevity, only techniques that apply to data objects residing in memory will be considered here. We strive to be respectful of peoples data plans and try to maximize the data sourced over unmetered connections. This paper provides a detailed evaluation on the energy impact of hardware data prefetching and then presents a set of new energyaware techniques to overcome prefetching energy overhead of such. Within sas there are numerous methods and techniques that can be used to combine two or more data sets. We commonly think that within the data step the merge statement is the only way to join these data sets, while in fact, the merge is only one of numerous techniques available to us to perform this process. One of our solutions was to add the users connection type into our logging events. Prefetching mechanisms for instructions and file systems are commonly used to prevent processor stalls, for example 24,20.
Optimizing computer runtime using data prefetching and code. Energyefficient hardware data prefetching nanoscale. Hardware and software cache prefetching techniques for. Zlib decompression, audio conversion and 3d vector calculation seem to get a bit of a benefit from a faster fsb, and a bit from the. Jouppi 1990 1 data stream buffer got 25% misses from 4kb cache. Lakshminarayana hyesoon kim richard vuduc college of computing georgia institute of technology atlanta, ga 30332 jaekyu. Deterministic prefetching for containermanaged persistence. Pdf machine learning techniques for improved data prefetching. My application form is already a pdf document but need to create a mail merge using data from excel and merge into the pdf document. In this assignment, you are required to explore data cache prefetching techniques using the intel pin simulation tool. Optimizing computer runtime using data prefetching and. Hardwarecontrolled prefetching initiated by processor executing a prefetch instruction programmer compiler hw prefetches at runtime. Pdf as the trends of process scaling make memory system even more crucial. Dec 11, 2006 you first have to determine whether you need prefetching at all.
In a previous paper we showed that prefetching and caching have thepotential to deliver the performance benefits of parallel file systems to parallel applications. Pdf on mar 24, 2015, diana guttman and others published machine learning techniques for improved data prefetching find, read and cite. A prefetching technique using hmm forward chaining for the. The idea of prefetching is to predict data access needs in advance so that a specific piece of data is loaded from the main memory before it is actually needed by the application.
Parallel disk io subsystems have been proposed as one way to close the gap between processor and disk speeds. A number of techniques exist for cache prefetching. Pdf a survey of recent prefetching techniques for processor. As previously stated, our btb structure takes advantage of stride prefetching. How to use the data prefetching competition kit jilp. In interthread prefetching, a thread prefetches data for other threads rather than for. Branchdirected and pointerbased data cache prefetching. Abstract merging or joining data sets is an integral part of the data consolidation process.
Using prefetching in conjunction with a cdn is good practice and often used to further speed up a websites load time. The future of prefetch memory latency isnt going away communicating access patterns to lower level architecture intel includes data speculation in itanium errors delivered on data use, not load schedule loads before stores raw avoidance. Although both involve a level of fetching data and storing it, they act in different capacities. Optimizing computer runtime using code optimization and data prefetching. Abstract this report covers techniques that are available to us to optimize the use of computer resources when doing image processing.
To store files in hdfs, many deduplication techniques are given but the existing techniques do not merge the unique small files the data nodetogether to improve the name node storage efficiency. Techniques for bandwidthefficient prefetching of linked data. Improvements in the processing speed of multiprocessors are outpacing improvements in the speed of disk hardware. Effective hardwarebased data prefetching for highperformance processors tienfu chen, member, ieee, and jeanloup baer, fellow, ieee abstractmemory latency and bandwidth are progressing at a much slower pace than processor performance. Improving performance with background data prefetching. In these models, various data prefetching techniques are combined with bdp. These techniques employ r1 r2 r3 r1 r2 r3 prefetch overhead no prefetching prefetching figure 3. In this paper, we describe and evaluate the performance of three variations of a.
Optimization techniques with case studies coalesced memory accesses data reuse through thread block merge. Data prefetching loadtogr0 loadhit instr time the problem avoid the loadmiss latency. Computer architecture hardware prefetching hardware monitors memory accesses looks for common patterns guessed addresses are placed into prefetch queue queue is checked when no demand accesses waiting prefetchers look like read requests to the hierarchy although may get special prefetched flag in the state bits. A central aspect of all cache prefetching techniques is their ability to detect and predict. While aggressive prefetching techniques often help to improve performance, they increase energy consumption by as much as 30% in the memory system. Manythread aware prefetching mechanisms for gpgpu applications jaekyu lee nagesh b. The data memory system modeled after the intel i7 consists of a 32kb l1 cache with a four cycle access latency. You are strongly advised to commence working on the simulator as soon as possible. Techniques for mitigating memory latency effects in the pa8500 processor. This paper proposes an alternative hardware scheme for prefetching, where a second processor is used solely for the purpose of prefetching data for the primary processor. An improved deduplication technique for small files in hadoop.
Speculative data prefetching for branching structures in dataflow programms sergiu carpov a,b,1 renaud sirdey a,1 jacques carlier b,1 dritan nace b,1 a cea list, embedded real time systems laboratory, point courrier 94, gifsuryvette, 91191 france. A survey of recent prefetching techniques for processor caches. The increasing gap between processor and main memory speeds hasbecome a serious bottleneck towards further improvement in system performance. If data order is linear then hardware prefetcher does its work and you by adding prefetch hints you actually hinder the performance. While a number of papers have been written studying both hardware and soft. Data prefetch mechanisms 177 acm computing surveys, vol. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Mckinley the memory hierarchy in modern architectures continues to be a major performance bottleneck. Without cache prefetching, data is transfered from the lower level of the. A branchdirected data cache prefetching technique for inorder processors.
Try to reogranize your data if you are seeing too many cache misses. Speculative data prefetching for branching structures in. How to use the data prefetching competition kit setting up the simulation infrastructure. In a hardware scheme the hardware predicts the memory access pattern and brings data into the cache before required by the processor. Other loadsstores use data in the same cache line as load a. Cache prefetching realtime and embedded systems lab. These prefetchers work well for sequential accesses through arrays and matrices, but for irregular, datadependent access 1section 4 gives more detail on benchmarks, graphs and experimental.
Effective hardwarebased data prefetching for highperformance. Combining local and global history for high performance. Practical prefetching techniques for multiprocessor file. You first have to determine whether you need prefetching at all. Stride prefetcher with prefetch bu er 2 prefetching cache prefetching is a technique to reduce cache miss rate by fetching data from memory to a cache before the data is actually needed. Cache prefetching is a technique used by computer processors to boost execution performance by fetching instructions or data from their original storage in slower memory to a faster local memory before it is actually needed hence the term prefetch. Our methodology is based on analyzing and automatically merging sql queries to produce query sequences with low total response time, in ways that exploit the applications data.
Hardware and software cache prefetching techniques for mpeg. Simple methods are used to isolate the sequential components of workloads, upon which prefetching is applied. Our goal in this paper is to develop techniques that 1 enable the efficient prefetching of linked data structures and 2 effi ciently combine such prefetchers with. Second, we propose two prefetching techniques, group prefetching and softwarepipelined prefetching, and show how they can be applied to signicantly improve hash join performance.
Software prefetching 2 is a tempting proposition for. Improving memory access performance of inmemory keyvalue. California occidental consultants, anchorage alaska. The prefetching techniques can be implemented to analyze the io from the client machine and then send the prefetching data to the relevant machine. A primary decision is made by utilizing previous tablebased prefetching mechanism, e. The jpeg and zlib compression tests seem pretty unfazed by either an fsb change or by the data prefetch logic. Prefetching mechanisms for instructions and file systems are commonly used to prevent processor stalls, for example 38,28. Merge excel data into pdf form solutions experts exchange. Combining local and global history for high performance data prefetching martin dimitrov and huiyang zhou. To store files in hdfs, many deduplication techniques are given but the existing techniques do not merge the unique small files the data nodetogether to. Prefetching pages means that one or more pages are retrieved from disk in the expectation that they will be required by an application prefetching index and data pages into the buffer pool can help to improve performance by reducing io wait times. Our results show that feedbackdirected prefetching eliminates the large negative performance impact incurred on some benchmarks due to prefetching, and it is applicable to.
Branchdirected and pointerbased data cache prefetching yue liu mona dimitri david r. However, these techniques do not work for irregular access patterns, as seen in linked data structures, and also in indirect memory accesses, where the addresses loaded are based on indices stored in arrays. Kaeli department of electrical and computer engineering northeastern university boston, ma abstract the design of the onchip cache memory and branch prediction logic has become an integral part of a microprocessor implementation. Manythread aware prefetching mechanisms for gpgpu applications. Improving the performance and bandwidthef ciency of hardware prefetchers santhosh srinathyz onur mutlux hyesoon kimz yale n. The prefetching techniques, uses hidden markov model forward chain and work distributed file system for cloud.
Data prefetching has been proposed as a technique for hiding the access latency of data. Each of these techniques has advantages and some have disadvantages. A performance study of software and hardware data prefetching. The l2 cache shared with instructions is 256 kb with a 10 clock cycle access latency. Nonblocking load instructions share many similarities with data prefetching. Data prefetching using dual processors springerlink. It has a high predictive accuracy and is extremely simple to implement. A survey of data prefetching techniques request pdf.
Subscribe to the prefetching competition mailing list by sending an empty email to dpc1subscribe at. Most modern computer processors have fast and local cache memory in which prefetched data is held until it is required. As noted in the article pcmark2002 a first look, some of these tests seem to have little or no reliance on memory accesses, while others do. Combining local and global history for high performance data. Code optimizations for high performance gpu computing. Techniques for mitigating memory latency effects in the pa. One other potential issue in determining the actual benefit of the data prefetch logic is the theoretical maximum bandwidth capability of the platform. Based on this observation, we explore various data prefetching techniques with proper architecture level modifications on memory controller considering trade. In this paper, we describe and evaluate the performance of three variations of a hardware function unit whose goal is to assist a data cache in prefetching data accesses so that memory latency is. Below are some of the techniques we apply to adapt the offline experience to different types of usage in.
874 332 1400 1152 170 475 1230 90 1365 971 1210 298 820 1170 889 1517 186 198 915 1463 392 701 318 677 949 215 442 927